医疗废物焚烧中二恶英的产生及控制

医疗废物的安全处置一直被世界各国所重视,我国自SARS灾难后,强化了医疗废物的治理力度。本文针对目前主要采用焚烧法处置医疗废物过程中二恶英的生成途径进行了论述,并结合二恶英的分子结构、毒性及危害提出了控制对策与建议。     

Effects of calibration on L-THIA GIS runoff and pollutant estimation

Urbanization can result in alteration of a watershed's hydrologic response and water quality. To simulate hydrologic and water quality impacts of land use changes, the Long-Term Hydrologic Impact Assessment (L-THIA) system has been used. The L-THIA system estimates pollutant loading based on direct runoff quantity and land use based pollutant coefficients. The accurate estimation of direct runoff is important in assessing water quality impacts of land use changes. An automated program was developed to calibrate the L-THIA model using the millions of curve number (CN) combinations associated with land uses and hydrologic soil groups. L-THIA calibration for the Little Eagle Creek (LEC) watershed near Indianapolis, Indiana was performed using land use data for 1991 and daily rainfall data for six months of 1991 (January 1-June 30) to minimize errors associated with use of different temporal land use data and rainfall data. For the calibration period, the Nash-Sutcliffe coefficient was 0.60 for estimated and observed direct runoff. The calibrated CN values were used for validation of the model for the same year (July 1-December 31), and the Nash-Sutcliffe coefficient was 0.60 for estimated and observed direct runoff. The Nash-Sutcliffe coefficient was 0.52 for January 1, 1991 to December 31, 1991 using uncalibrated CN values. As shown in this study, the use of better input parameters for the L-THIA model can improve accuracy. The effects on direct runoff and pollutant estimation of the calibrated CN values in the L-THIA model were investigated for the LEC. Following calibration, the estimated average annual direct runoff for the LEC watershed increased by 34%, total nitrogen by 24%, total phosphorus by 22%, and total lead by 43%. This study demonstrates that the L-THIA model should be calibrated and validated prior to application in a particular watershed to more accurately assess the effects of land use changes on hydrology and water quality.     

The impact of government subsidy and tax policy on the competitive decision-making of remanufacturing supply chains

In this paper, we consider a two-period competition model of a remanufacturing supply chain consisting of three members: a new product manufacturer, a recycler and a remanufacturer. The manufacturer supplies new products in the first period and the remanufacturer participates in the competition in the second period. We consider three scenarios in the second period: (1) there is no government subsidy in the competition; (2) there is only government subsidy in the competition; (3) there are both government subsidy and tax in the competition. First, we give the optimal decision-making of the manufacturer, the remanufacturer and the government in the three scenarios; second, we analyse changes in the decision-making of the manufacturer and remanufacturer in the three scenarios and compare their results. We analyse the effects of government subsidy and tax and their asymmetric use on manufacturers’ and remanufacturers’ decision-making variables and competitive performance. We also take consumer awareness of environmental protection into account and examine its impact on subjects’ decisions. Lastly, we operate a numerical example to show the results.     

Determination of the residue dynamics and dietary risk of thiamethoxam and its metabolite clothianidin in citrus and soil by LC-MS/MS

A modified quick, easy, cheap, effective, rugged and safe (QuEChERS) method was developed for the determination of thiamethoxam and its metabolite clothianidin in citrus (including the whole citrus, peel and pulp) and soil samples by liquid chromatography-tandem mass spectrometry. The sample was extracted with acetonitrile and purified with octadecylsilane. The detection limits of both compounds were 0.0001–0.0002?mg kg^–1, while the limit of quantification of thiamethoxam was 0.002?mg kg^–1 and the limit of quantitation of metabolites was 0.001?mg kg^–1. The recovery was 70.37%–109.76%, with inter-day relative standard deviations (RSD) (n?=?15) values ≤9.46% for the two compounds in the four matrices. The degradation curve of thiamethoxam in whole citrus and soil was plotted using the first-order kinetic model. The half-life of the whole citrus was 1.9–6.2?days, and the half-life of the soil was 3.9–4.2?days. The terminal residue of thiamethoxam (the sum of thiamethoxam and clothianidin, expressed as thiamethoxam) was found to be concentrated on the peel. The final residual amount of thiamethoxam in the edible portion (pulp) was less than 0.061?mg kg^–1. The risk quotient values were all below 1, indicating that thiamethoxam as a citrus insecticide does not pose a health risk to humans at the recommended dosage.     

嘉陵江有毒鱼类的分布研究

为了丰富人们对有毒鱼类的认知,结合8年的调查数据和已有资料对嘉陵江中有毒鱼类的种类、分布和食性进行研究。研究结果发现:在嘉陵江中有毒鱼类共计18种,隶属于4目6科17属,随着分类水平的变化(从目、科、属到种),有毒鱼类在不同分类级别下所占的比例逐渐降低。嘉陵江有毒鱼类中仅圆口铜鱼(Coreius guichenoti)和鳜(Siniperca chuatsi)分布于中下游,其余16种有毒鱼类分布于整个嘉陵江干流。Jaccard’s相似性分析表明各江段有毒鱼类分布的相似性极高,卡方(χ~2)检验结果显示各江段有毒鱼类分布无显著性差异(p0.05)。嘉陵江分布的有毒鱼类共4类,包括卵毒鱼类2种,血清毒鱼类1种,胆毒鱼类9种以及刺毒鱼类7种,其中鲇(Silurus asotus)既属于卵毒鱼类也属于刺毒鱼类,胆毒鱼类全部来源于鲤科鱼类,暂没有发现皮肤黏液毒鱼类。这18种有毒鱼类共包含7种食性类型,主要以杂食性和肉食性类型为主,分别占有毒鱼类种类数的38.89%和33.33%。通过本研究可知,有毒鱼类在嘉陵江中分布广泛,有毒鱼类种类和类别较多。该研究促进了人们对嘉陵江有毒鱼类相关知识的了解,为进一步研究嘉陵江有毒鱼类奠定了基础。     

非点源污染河流的水环境容量估算和分配

通过河流相应集水区内氮磷的各污染源分析(包括农地、畜禽养殖和生活排污等),利用输出系数模型估算各非点源的氮磷投(排)放量和入河量;采用河段氮磷输入-输出平衡关系分析方法,估算河流对氮磷的每月自净量.以此为基础,参照水功能区划所要求的水质目标,提出了水质未超标河段相应集水区的氮磷剩余水环境容量按月估算模型,和水质超标河段相应集水区内氮磷投放削减量的按月估算模型,及其在各污染源之间的分配方案.结果表明,长乐江的总氮和总磷自净量分别达到775.9 t·a^-1和30.9 t·a^-1,自净率分别为28.8%和51.2%.河流对氮磷的自净量不仅受水文生态条件的影响而表现出较大的季节性变化,而且随着污染负荷量本身的增加而提高.按照水功能区划中Ⅲ类水的水质要求,长乐江总氮含量全年超标;各非点源的总氮投(排)放量均须不同程度的削减,削减总量应达到1 581.0　t;氮源削减量分配结果表明,化肥是应削减的最大氮源,要求在河流相应集水区内的化肥氮投放削减量为1 047.4 t·a^-1;而与各种氮源的投排放现状相比,要求削减比例最高的是畜禽养殖的氮排放量,达32.4%.长乐江流域尚有一定的总磷剩余水环境容量(2 335.7 t·a^-1).根据目标水质要求,平水期是各污染源总氮投放需要削减的量最大的时期,丰水期则是总磷剩余水环境容量最小的时期.     

La2O3-CeO2/γ-Al2O3催化剂还原脱硫耐氧特性及其反应机理研究

用浸渍法制备了一系列稀土催化剂,研究了其催化CO还原SO2为单质硫的耐氧特性及影响其耐氧性能的主要因素,运用XRD技术分析了催化剂物相的变化及脱硫产物成分.结果表明,12% La2O3-8% CeO2/γ-Al2O3复组分催化剂比其他La2O3-CeO2/γ-Al2O3催化剂具有更好的耐氧性能;脱硫温度、催化剂用量、SO2与CO的摩尔比等对催化剂的耐氧性能均有明显的影响.最后,探讨了稀土催化剂脱硫机理,并分析在有O2条件下,引起脱硫率下降的原因是反应过程中O2与CO、S发生了竞争性反应.     

铁屑去除酸法地浸采铀地下水中硝酸盐的试验研究

在酸法地浸采铀过程中,硝酸及硝酸盐的广泛使用使硝酸盐在地下不断累积并扩散到地下水中,这给矿区地下水造成了一定程度的污染.本试验以铁屑为还原剂,对该地下水中NO3--N的去除进行了批试验和动态试验研究.试验结果表明,铁屑可有效去除地下水中的NO3--N,其去除率随pH值的降低而逐渐升高;溶液中共存的Ca2 、Mg2 对NO3--N的去除影响不大,而SO42-、HCO3-的存在可明显降低NO3--N去除率;铁屑最佳投加量为120 g/L,铁炭最佳体积比为1∶1;二级柱可以明显提高柱子的稳定运行时间,在55 h内NO3--N去除率可保持在93%以上,去除效果较好.     

《燃煤二氧化硫排放污染防治技术政策》绩效定量评估

基于全国46个城市(其中38个城市位于"两控区")1996~2005年的面板数据,运用difference-in-differ-ences(DID)模型对《燃煤二氧化硫排放污染防治技术政策》的绩效进行了定量评估。结果表明,该政策的实施对于降低工业二氧化硫排放量起到积极作用,使"两控区"城市年工业二氧化硫的排放量平均降低了19.3%。     

超滤处理洗涤污水循环利用的中试研究

采用不同材质国产超滤膜聚丙烯（PP）、聚丙烯腈（PAN）和聚砜（PS）,进行了洗涤污水处理循环利用的现场中试研究.结合超滤工艺出水水质和膜污染分析,3种膜材质中PAN膜较优,有效去除了水中浊度、悬浮物、油脂等污染物,一定程度保留了游离阴离子表面活性剂（LAS）,长期循环洗涤对衣物的白度无不良影响.根据相关性分析,超滤出水较高COD值很大程度上是由水中LAS引起的.超滤膜对细菌、大肠菌群的去除率较低,出水通过紫外消毒,当紫外线密度≥3?750 J/m²时,微生物水平能够达到国家饮用水水质标准.根据不同水力反冲洗条件下膜渗透通量和净产水量比较,PAN膜最佳水力反冲洗条件为0.5 h反冲洗2 min.长期运行时超滤膜化学清洗方法采用碱洗法方便有效.